In an effort to protect vehicle operators and occupants, vehicle manufacturers and their suppliers are increasingly designing and manufacturing vehicles with additional and improved safety features. One such safety feature that has been incorporated into a number of vehicle types is anti-lock braking, which can take a variety of forms.
Vehicle anti-lock brake systems are designed to maximize the ability of a vehicle operator to bring a vehicle to a controlled stop on any type of road surface. The system accomplishes this goal by preventing the vehicle brakes from prematurely halting vehicle wheel rotation, or "locking" the vehicle wheels, regardless of the road surface and the pressure applied to the brake pedal by the vehicle operator.
Referring now to FIG. 1, a schematic diagram of a motor vehicle is shown, denoted generally by reference numeral 10, in conjunction with a prior art passenger vehicle anti-lock brake system (ABS). The vehicle 10 has mounted therein a brake pedal 12, a brake switch 13, a brake master cylinder 14 operated by the brake pedal 12, control valves and pump, collectively indicated at 16, brake fluid conduits 18, 20, 22, 24, 26 and 27 as well as a right front wheel 28, a left front wheel 30, and a pair of rear wheels 32.
A pair of vehicle wheel speed sensors 34 measure the velocity of each of the front wheels 28 and 30, and a pair of vehicle wheel speed sensors 36 measure the velocity of each of the rear wheels 32. The ABS further includes an ABS electronic control unit 38. The control unit 38 typically includes one or more commercially available microprocessors.
Each of the wheel sensors 34 and 36 are operatively connected to the control unit 38, which is itself operatively connected to the anti-lock brake system power relay at 16. Such operative connections are preferably electrical, but may also be other types of connections, such as fiber optic.
As is well known in the art, each of the wheel speed sensors 34 and 36 may comprise a stationary variable reluctance sensor (not shown) positioned adjacent a toothed wheel (not shown) which rotates with its respective vehicle wheel 28, 30, 32. The variable reluctance sensors each generate a pulsed signal whose frequency varies directly with the speed of the respective vehicle wheels 28, 30, 32. Other well known wheel speed sensor configurations may also be employed.
Many vehicle programs include numerous vehicles and vehicle configurations. One result of such a large number of configurations is that numerous software versions are required where the difference is only due to trim constants which are different to compensate for different vehicle parameters such as wheel-tire inertia, load variation, brake sizes, center of gravity location, or suspension. Another reason to have numerous software versions is to obtain desired performance characteristics for different vehicle applications. As a result, numerous types of control units must be stocked.
The patent to Otobe (U.S. Pat. No. 4,829,439) provides a method of selectively adapting an electronic control unit for an internal combustion engine. An ECU is modified after installation to reflect either a manual or standard transmission.
The patent to Carp et al. (U.S. Pat. No. 4,623,976) provides an automatic calibration selection for an automobile control system which allows the use of a single ECU for a family of motor vehicles. External selection of a particular ROM address allows for adaptive calibration set selection. The patent to Sinn (U.S. Pat. No. 4,908,760) uses a similar calibration strategy in a self-cleaning oven temperature control system.
The patent to McMahon et al. (U.S. Pat. No. 5,265,576) provides a master calibration set stored in an electronic control unit. The ECU master calibration set is modified by a separate calibration adjustment system to adjust for actual performance characteristics.
The patent to Paielli (U.S. Pat. No. 5,091,858) provides an electronic engine control unit (ECU) including a plurality of look-up tables. The system further includes a means to selectively vary the control parameters by initiating a programming mode of operation to up-load new tables.
The patent to Byrne et al. (U.S. Pat. No. 4,700,304) provides a ROM, typically an EPROM, which controls ECU microprocessor testing and resetting in an anti-skid braking system.
The patent to Watanabe (U.S. Pat. No. 4,478,193) provides a method of easily changing calibration data stored in a back-up Ram of an electronic control unit (ECU) for an internal combustion engine.
The patent to Otobe et al. (U.S. Pat. No. 4,618,954) provides a fault diagnosis system using an electronic control unit wherein internal calibration control parameters are dynamically substituted for malfunctioning sensors to prevent erroneous operation.
The patent to Regueiro (U.S. Pat. No. 5,313,924) provides an electronic control unit which can be programmed to accommodate various engine environmental and state conditions for optimal engine performance.
One problem associated with the prior art is that the wrong set of calibration data may be selected and, consequently, the ABS may not be properly calibrated for the vehicle being controlled.